One of the world's most powerful drug traffickers during the 1990s is scheduled to be sentenced to prison in San Diego.

Federal prosecutors are seeking a 25-year sentence Monday for Benjamin Arellano Felix _ the longest allowed under a plea agreement reached in January. It would be a lighter punishment than ordered for lower-ranking members of his once-mighty Tijuana-based cartel.

In an 11th-hour twist, the 58-year-old fired his attorney, fueling speculation that he may be having second thoughts about his guilty plea. His new attorney hasn't filed any court documents indicating what sentence he will seek.

Arellano Felix was extradited from Mexico in April 2011, nine years after his arrest there. He is one of the highest-profile kingpins to face prosecution in the United States.